In the prior art, devices are known that permit a user having a terminal and a connection to a server of audio-visual information to download pieces of music in order to listen to them in real time or to store them in data storage means, either connected to the terminal, or transportable so as to be able to play them back or duplicate the pieces of music an unlimited number of times. However, most of these devices do not permit the calculation of royalties due to those having rights to the pieces of music since none of these devices enable the use made of the piece of music to be verified.